Safety device for power presses



Dec. 5, 1961 A. l. STIEBEL ET AL 3,011,610

SAFETY DEVICE FOR POWER PRESSES Filed Oct. 9, 1959 4 Sheets-Sheet 1 I NV EN TORJ 42/51 Z @vzzn f1 7 4 BY m w yZ/%wr%a2 Dec. 5, 1961 A. 1.STIEBEL ET AL 3,011,610

SAFETY DEVICE FOR POWER PRESSES Filed on. 9, 1959 4 Sheets-Sheet 2 IN VEN TOR-5 F/AZ [Jr/[ea Dec. 5, 1961 A. 1. STIEBEL ETAL 3,

SAFETY DEVICE FOR POWER PRESSES Filed Oct. 9, 1959 4 Sheets-Sheet 3 #7me. 3 H

Dec. 5, 1961 A. 1. STIEBEL ET AL 3,011,610

SAFETY DEVICE FOR POWER PRESSES Filed Oct. 9. 1959 4 Sheets-Sheet 4 INVEN TOR5 49/51 [Jvzea ATTORNEYS United States Patent O1 3,011,610 SAFETYDEVICE FOR POWER PRESSES Ariel I. Stiehel, Detroit, and Miles G. Rigby,Birmingham, Mich, assignors to Rockwell-Standard Corporation,Coraopolis, Pa., a corporation of Pennsylvania Filed Oct. 9, 1959, Ser.No. 845,524 3 Claims. (Cl. 192-131) This invention relates toimprovements in automatic safety devices for power machines and is moreparticularly concerned with electrically operated safety devices foroperator-actuated power presses.

This application is a continuation-in-part of the copending applicationSerial No. 757,581 filed August 27, 1958.

In the power machine art, and more particularly with relation to punchand forming presses, it is customary to provide a cross-head or otherwork forming element reciprocating with respect to -a bed plate andhaving power machinery for effecting such reciprocation, so as toproduce punching and forming operations in the machine. As usuallyconstructed, the machine has a vertical reciprocating cross-headactuated by a crank shaft or other similar device on which there ismounted a large and heavy fly wheel, the fly wheel being in turnactuated by an electric motor or other power source. Such machines areconstructed so as to include a clutch mechanism between the fly wheeland the crank shaft driven by the fly wheel so that during suchintervals when the clutch mechanism is disengaged and the machine is notoperating, the motor or other power source which supplies the motivatingforce is permitted to build up the speed of the fly wheel. When theoperator desires to cause the cross-head and the tools that it carriesto descend upon the bed plate in cooperating relation with the formingdies of the bed plate, he actuates a control which is usually in theform of a treadle positioned near the base of the press so that it canbe operated by the operators foot leaving the operators hands free tohold or manipulate materials in and out of the power press. Actuation ofthe treadle engages the clutch and the stored energy of the fly wheelcauses the crank shaft to turn and the cross-head to go through aworking stroke.

This foot treadle control has been the cause of end less and seriousaccidents because the operators, after some period of work at themachine, tend to become careless and permit their fingers or hands tomove into the path of actuation of the die forming element of themachine. A particular practice of some operators is to ride the treadleand attempt to time the insertion and removal of materials in and out ofthe machine in accordance with the cyclic speed of the machine, orattempt to manipulate parts into and out of the machine after it hasstarted to move. As a result of these unsafe practices, serious injuryhas been experienced in many instances with respect to the arms andhands of the operators.

In the past, it has been proposed, in an effort to achieve safer workingconditions, to provide hand controls which must be actuated by bothhands of the operator andv held actuated in order to cause the machineto move. Such controls, while contributing to the safety of theoperator, cause serious loss in production since the operator mustoperate the machine with his hands in addition to transferring materialsin and out of the machine.

Other safety expedience presently on the market are inherentlydisadvantageous in that the machine may be run by the operator withoututilizing the protective mechanisms provided. Thus, the safety factorinvolved in employing such devices depends entirely upon the will of theoperator in deciding whether or not he will make use of the deviceprovided for his safety.

3,9?!1 ,iilll Patented Dec. 5, 1961 An example of these prior devices isdisclosed in the United States Letters Patent to Possons No. 1,417,346dated May 23, 1922 wherein it is proposed that a safety pull-out guarddevice comprising a pair of cuffs to be worn by the operator and havingcable connections between the cuffs and the movable forming element ofthe press be employed to forceably withdraw the operators hands from adangerous position adjacent to or over the work area during theactuating period and work forming cycle of the machine. This device anda great majority of similar expedients present the inherent disadvantagein that the press may be run by the operator without utilizing theprotective mechanism provided for his safety.

Accordingly, it is the primary object of the present invention toprovide an improved form of the ?ossons safety device for use in poweroperated machines having a movable work forming element controlled by atreadleactuated clutch mechanism wherein a clutch controlling treadle isren ered inoperative to actuate the clutch mechanism whenever the safetyguard pull-away cable connections are not secured to the cuffs retainedabout the operators wrists Thus, where the operator has omitted toattach the pull-away cables to his safety wrist cuffs throughinadvertence or for other purposes, the clutch-controlling treadle isrendered inoperative to effectuate movement of the work forming elementand the machine, therefore, cannot be operated by actuation of theclutch controlling treadle.

In accordance with the present invention this is accomplished byproviding electrical switches in an electrical control circuit for thepower operated machine which are actuated by attaching the safety cablesto cufis worn about the wrists of an operator. Actuation of theelectrical switches energizes the control circuit which, in turn,functions to energize an electromagnetic coupling device operablycoupling the control treadle to the clutch mechanism so that depressionof the control treadle actuates the clutch mechanism to transmit powerfrom a supply source to the work forming element to move the latterthrough its cycle of operation.

The safety cables when attached to the wrist cuffs are secured theretoin such a manner as to prevent the removal of the cuffs by the operator,and function to pull the operators hands away from the work area duringa selected cycle of the operation. Consequently, to move away from themachine or to remove the wrist cuffs, the operator must first detach thesafety cables to thereby render the machine inoperative by actuation ofthe operating foot treadle.

With the foregoing purposes and considerations in mind, therefore, it isa further major object of this invention to provide for a novel safetydevice for operatively disconnecting a control treadle of a poweroperated machine so as to render the treadle inoperative to set the workforming element of the machine in motion.

A further object of the present invention is to provide in a poweroperated machine equipped with a foot treadle actuated clutch, a novelsafety device which includes the safety device according to ourco-pending application Serial No. 757,581 and functions to operativelyconnect the foot treadle to the clutch whenever the safety device ofsaid co-pending application is properly afiixed to the body of theoperator.

It is a further object of this invention to provide in a power operatedmachine equipped with a foot treadle adapted to be actuated by anoperator for controlling the operation of the machine, a novelelectromagnetic coupling device which is operative when energized topermit operation of the machine with the treadle and which isenergizable by an electrical control circuit when the safety 3 device inaccordance with our said co-pending application is mounted to respond tothe movement of the work forming element of the machine and attached toa selected part of the operators body.

A further object of the present invention resides in the provision ofthe electromagnetic coupling device of the preceding object wherein anovel guide screw construction assures self alignment between the coreand the armature of the coupling by allowing limited side or lateralmovement of the armature relative to the core and, at the same time,prevents the coupling from turning.

A further object of the present invention is to provide in a powerdriven machine having a work holding bed, a

work forming element movable into and out of working relation with thebed, a power source for driving the work forming element, a clutchmechanism operably connecting the power source to the Work formingelement and a manually operated clutch operator for selectivelyactuating the clutch mechanism to control the movement of the workforming element by operatively engaging and disengaging the clutchmechanism, a novel safety device having safety cable connections adaptedto be detachably latched to wrist cuffs retained about the Wrists of anoperator and responsive to the movement of the work forming element forforceably withdrawing the hands of .the operator to a place of safetyduring the work forming stroke of the work forming element, anelectromagnetic coupling device operable when energized to cou ple theclutch operator tothe clutch mechanism, and a special electrical controlcircuit for de-energizing the coupling device whenever the safety cableconnections are unlatched from the wrist cuffs.

Further objects of the invention will presently appear as thedescription proceeds in connection with the appended claims and theannexed drawings wherein:

FIGURE 1 is an elevational View Of a power press provided with a safetydevice for operating an electromagnetic coupling according to oneembodiment of the present invention;

FIGURE 2 is an enlarged front elevation partly in cross section of theelectromagnetic coupling of FIG- URE-l;

FIGURE 3 is an enlarged side elevation partly in cross section takensubstantially along line 3-3of FIGURE 2;

FIGURE 4 is a cross section showing the support for the magneticcoupling of FIGURE 1 and taken substantially along the line 44 of FIGURE2;

FIGURE 5 is a cross section of the magnetic coupling taken substantiallyalong'line 5-5 of FIGURE 2;

FIGURE 6 is a schematic wiring diagram of the electrical control circuitfor the embodiment illustrated in FIGURE 1;

FIGURE 7 is a perspective view of the safety cable hook assemblyattached to a cuff fastened about the wrist of the operator; and

FIGURE 8 is an elevation of the safety hook connection of FIGURE 7having the side wall of the hook housing removed.

Although the construction embodying the principles of the presentinvention is shown and described in its application to a power press,the present invention further contemplates the utilization of the novelsafety device hereinafter described generally for operator actuatedpower machines where there is a danger of injury occurring to theoperator by coming in contact with the moving parts of the machine. Forexample, the present invention may be applied with respect tofacilitating the safe operation of dye presses, stamping machines, andis particularly adapted wherein work pieces are moved by the operatorinto and out of the machine which has movable parts to perform someoperation on the piece.

Thus, with reference now to the drawings and more particularly to FIGURE1, wherein the construction emat 20 is illustrated to comprise asuitable cast base 22 upon which is mounted by bolts 23 a cast frame 24for supporting the working parts of the press. Afiixed to the lowerportion of the frame '24 by any suitable means is a conventional bedplate 26 towhich a stationary lower die 28 is removably secured forreceiving a work piece (not shown). A cross head 30 provided with anupper die 32 is mounted for vertical reciprocal movement in alignmentwith the lower die 28 and bed plate 26 and is connected by a suitablyjournalled crank shaft 34 through a conventional clutch 36 such asastandard pressure-plate type to a flywheel 38. The flywheel 38 ismounted for rotation on the frame 24 and is drivingly connected by abelt 40 to a pulley (not shown) arTixed on an output shaft (not shown)of an electric motor 42 or other suitable prime mover.

In order to enable the operator to selectively actuate the clutch 36 toreciprocate cross head 36 so that the dies 28 and 32 engage and form thework piece positioned on the lower die 28, an operating foot treadle 58is provided having one end pivotally secured to the lower portion of thebase 22 as by pin 52. The treadle St) is biased to an upper disengagingposition by a coil spring 54 which is secured at its upper end to thebase 22 by a machine screw 56 and which is provided with a hook end 58extending through ring 59 secured to the treadle 56 intermediate theends thereof. Between the pivoted end at 52 and the spring connection at59, an upstanding rod 6% is pivotally connected at one end to the foottree le 5% so that it is movable with the treadle 50 as the treadle isdepressed by the operator against the bias of the spring 54.

Referring now to FIGURES 1-5, the upper end of the rod 60 terminates ina threaded section which is threadedly received in a turnbuckle 62(FIGURES 2 and 3). The opposite end of turnbuckle 62 threadedlyreceives, a short screw rod 64 which slidably extends through a guidebushing 66 and threadedly engages the cross piece of a soft ironhorseshoe core768 of an electromagnetic coupling 79 which willhereinafter be described in detail.

T he guide bushing is provided with an externally threaded section 72which is threadedly received through a centrally located aperture formedin the laterally extending ear 74 of a U-shaped bracket 76. The guidebushing 66 extends beyond the car 74 and is secured in place bytightening and lock nuts 78 and 80. This U-shaped bracket 76 supportsthe magnetic coupling 70 and is affixed to the frame 24 by bolts 82which extend through the cross piece 84 of the bracket.

In accordance with the present invention, the magnetic coupling 70functions to operatively disconnect the foot treadle 50 from the clutch36 to thereby prevent operation of the cross head 30 by actuation of thefoot treadle 59 as will become apparent. The core 68 of magneticcoupling 7tlis a conventional horseshoe type core having parallelupstanding legs 86 and 88 which are joined together by an integral crosspiece 96. The cross piece 90 is formed with a centrally locatedinternally threaded through bore which receives the threaded end sectionof rod 64 so that the cross piece 90 is supported on an annular shoulder92 formed by rod 64. To establish a magnetic flux in the core 68,conventional coils 9 4 and 96 of a suitable number of turns respectivelyare wound around each core leg 86 and 88. The rectangular barshapedarmature 98 of coupling 70 which is attracted by the core 68 when thecoils 94 and 96 are energized, is formed with a centrally locatedinternally threaded through bore which threadedly receives the reduceddiameter end threaded section of a rod 100. This armature 98 spans thelegs 86 and 88 of the core 68, and has the same width and spanned lengthas core 68 so that, in assembled relationship, the vertical faces of thearmature are in the same mutually perpendicular vertical planes passingthrough the vertical surfaces of the core 68.

' In order to facilitate alignment of armature 98 with the core 60, theupper lateral car 102 of U-shaped bracket 76 overlying the armature 98is formed with two opposed centrally located slots 104 and 106 as bestillustrated in FIGURE 4. Two elongated guide screws 108 and 110respectively freely extend downwardly through slots 164 and 186 andthrough enlarged bores 112 and 114 provided in the armature 98 andthreadedly engage in internally threaded bores extending inwardly fromthe exposed planar end faces of the core legs 86 and 88. The throughbores 112 and 114 provided in the armature 93 respectively with slots104 and 196 and the slots 104 and 106 and bores 112 and 114 are oflarger diameter than the screws 108 and 119 to provide for a free andrelatively loose guiding fit therewith. As a resu'lt of this novelcoupling guide screw construction, selfalignment of the coupling 70 isassured by limited side or lateral movement of the armature 98 relativeto the core 68 and, at the same time, the coupling is prevented fromturning.

The rod 169 is aligned with and slidably extends through an upper guidebushing 116 formed with a threaded section 118 which is threadedlyreceived through a centrally located aperture formed in the upperlateral ear 192 of bracket 76 and extends beyond the top thereof toreceive tightening and lock nuts 120 and 122 respectively. The guidebushing 116 is in axial alignment with guide bushing 66 and both guidebushings 66 and 116 provide a loose sleeve bearing fit for rods 64 and100 respectively to maintain the armature 98 in substantial linearalignment with the core 68.

With continued reference to FIGURES 1-5, the linkage connecting the rod100 to the cross head clutch 36 comprises a cylindrical adaptor 124threadedly afiixed to the upper end of screw rod 100 and formed with ayoked end 126. The lower end of a link 128 is positioned between thelegs of the adaptor yoked end 126 and is pivoted on a pin 129 carried bythe yoked end 126.

The upper end of link 128 is pivotally mounted about an axis formed bybolt 130 of a bolt and nut assembly 132 carried by the yoked end 134 ofa force multiplying lever 136. The force multiplying lever 136 iscentrally fulcrummed about a machine screw 138 which is threadedlysecured to the cast frame 24. The opposite righthand end of lever 136 asviewed from FIGURE 1 is suitably afiixed to the lower end of anupstanding rod 140 which has its upper end pivotally secured to theouter end of a horizontally extending clutch disc shifting rod 142 whichfunctions to actuate the clutch 36 between engaged and disengagedpositions.

By this construction, it will be appreciated that depression of the foottreadle 50 by the operator'shifts rod 60 downwardly. When the coils 94and 96 of magnetic coupling 70 are energized, the armature 98 isattracted to the core 68 so that when the core 63 is shifted downwardlywith rod 60 the armature is also shifted with it. This motion shiftslink 128 to rotate the force multiplying lever 136 about its pivotalaxis 138 from the dotted line position indicated at 144 (FIGURE 2) tothe solid line position shown in FIGURES l3. This movement shifts rod149 upwardly to move the clutch disc selector rod 142 so that the discs(not shown) of clutch 36 move into engaging position whereby theflywheel 38 is operatively coupled to cross head 30 through shaft 34.

The shift rod 142 may be spring suspended by means not shown so as to bebiased to a clutch releasing position.

In order to electrically control the operation of the magnetic coupling79, an electric control circuit 150 is provided as shown in FIGURE 6 andcomprises a transformer 152 having a primary winding 154 connecteddirectly to a source of alternating current voltage and a secondarywinding 156 connected to taps 158 and 160. The transformer 152 functionsto reduce the line voltage generally 117 volts) to an acceptable controlcircuit voltage (generally 6 volts) and also thereby eliminates thepotential hazard of electrical shock to the operator of press 20 as willbecome aparent. The secondary winding 156 is connected to an electricalcircuit which includes a relay 162 having a solenoid coil 164 connectedacross the secondary winding terminals 158 and by conductor 166 andconductor 168.

With continued reference to FIGURE 6, the relay 162 is provided with anarmature 170 which is adapted to move a pair of mechanically interlockedswitch blades 172 and 174. When the relay 162 is deenergized, the switchblade 174 is biased (by means not shown) to engage a stationary switchcontact 176 and the switch blade 172 is biased (by means not shown) tobe out of engagement with an associated stationary contact 178. Whenrelay 162 is energized the switch blade 172 moves into engagement withits associated contact 178 and the switch blade 174 is disengaged fromits associated contact 176. When switch blade 172 engages switch contact178, an energizing circuit is serially completed through switch blade172 and contact 178 to the primary winding 18% of a stepdown transformer182 which is connected across a source of alternating current voltage,not shown.

With reference now to FIGURES 2, 3 and 6, the fixed terminals of thesecondary winding 184 of the stepdown transformer '182 are connectedby'conductors 186 and 188 respectively to terminals 190 and 192 mountedin a terminal plate 194 which is fixedly secured to the U- shapedbracket '76 as by screws 196 (FIGS. 2 and 3). The terminals 190 and 192are suitably electrically insulated from the terminal plate 194 and areeach respectively connected to one end of magnetic coupling coils 94 and96 by conductors 197 and 198. The other ends of the coils 94 and 96 areconnected together to establish a circuit that may be traced from thesecondary 184, through the conductor 186 to terminal 191?, throughconductor 197, through coil 94, through coil 96, through conductor 198to terminal 192, and through conductor 188 to the secondary 184.

With continued reference to FIGURE 6 a resistance 199 of suitablecapacity is interposed in conductor 166 in series circuit relationshipwith the solenoid coil 164. Switch blade 174 and stationary contact 176are connected in parallel to the resistance 199 by means of conductors288 and 291 which respectively connect switch blade 174 and contact 176to conductor 166. Thus, when the relay 162 is deenergized and switchblade 174 moves into engagement with contact 176, the parallel circuitestablished through conductor 208, switch blade 174, contact 176 andconductor 28 1 functions to bypass the current flowing to energize therelay 162 around the resistance 199.

The capacity of resistance 199 is such to reduce the magnitude ofcurrent in control circuit 150 to a minimum value for retaining solenoid164 with its armature 170 in energized position as long as continuity ismaintained in the energizing circuit. Thus, the resistor 199 with theparallel switch 174 functions to prevent excessive heating and potentialburn-out of the coil 164 whenever a power failure or break in thetransformer second ary occurs since the circuit is shunted through theresistor 199 whenever the solenoid coil 164 is energized.

Since the capacity of resistor 199 is such to reduce the value of thecurrent in the control circuit to a minimum holding current forretaining the armature 170 in energized position, it will be appreciatedthat any interruption in the control circuit 151 results in an immediateand positive action to deenergize the solenoid relay therebyinterrupting current flowing through primary winding which serves toenergize the magnetic coupling 71 and thereby renders the pressinoperative. Thus, whenever the control circuit 158 is interrupted bythe selected operation or by a power failure, the armature 170 is movedto its deenergized position immediately upon the '3 initial drop incurrent to disengage switch blade 172 from its associated contact 178 soas to deenergize the secondary load circuit of transformer 182.

Energization of relay 162 is controlled by a pair of microswitches 204and 266 which are interposed and connected in series in conductor 168between the transformer secondary terminal 158 and one end of thesolenoid' coil 164. These microswitches 284 and 286215 shown in 'FTGURE8 are identical to the spring-loaded pin actuated microswitch structuredisclosed in our copending application S.N. 757,581.

By this circuitry it will be apparent that if either of the switches 204or 206 are open, no current will flow through the solenoid coil 164.Thus, the stepdown transformer 182 and consequently the coils 94 and 96of magnetic coupling 70 remain deenergized to render 'the foot treadlet} inoperative to engage the clutch 36 for operating the cross head 30of punchpress 29.

In accordance with the present invention, the microswitches 204 and 206are actuatable by a safety device generally indicated at 208, whichfunctions to forceably withdraw the operators hands from a dangerousarea adjacent to and over the work area and from around the die 28 andbed plate 26. This safety device 208 is identical to the structure shownand disclosed in our said copending application Serial No. 757,581 thedisclosure of 'Which is hereby adopted and incorporated herein byreferencet Safety device 268 according to the principles of saidcopending application comprises an upright standard 210 fixedly securedto the floor at a convenient space distance apart from the punch press29 and to the left thereof as shown in FIGURE 1. With continuedreference to FIGURE 1, standard 210 terminates in a sleeve 212 whichsupportingly receives one end of a horizontally extending cross rail214. The cross rail 214 is fixedly secured in sleeve 212 as by setscrews 216 and is supported at the other end thereof in a recessedadaptor 218 affixed to the cast frame 24. A rocker arm 220 rotatableabout a fixed pivot 222 on cross rail 214 intermediate the ends thereofis provided with an integral gear segmentv224 which meshes with rackteeth 226- formed at the upper end of a connecting rod 228. Theconnecting rod 228 is rigidly secured at its lower end to the cross head30 as by machine screws 238 for reciprocal movement therewith.

Afiixed to rocker arm 22% is a flexible cable 232 which passes over asheave 234 rotatably mounted about a pin 236 rigidly supported by thestandard 210'. Cable232 extends down through a tubular guide 238 securedto the standard 210 and branches into two separate flexible cables 249and 242 below the tubular guide 238. Each of the branch cables 249 and242 is pivotally connected at 245 to a safety hook assembly 244 as shownin FIGS. 7 and 8. These safety hook assemblies 244 are of identicalstructure as the structure shown in our said copending applicationSerial No. 757,581 and house micro switches 294 and 206 schematicallyshown in FIGURE 6. With continued reference to FIGURE 8, each of themicro switches 284 and 286 are actuatable to closed po sition by aflexible spring arm 246 which extends across the gap of the hook 248and-is fixedly secured at one end to a casing 250 mounting the microswitch.

Referring now to FIGURES 1, 7 and 8, safety hook 248 is adapted to beremovably attached to rigid ring staples 252' of wrist cuffs 254 whichare retained about the Wrists of the operator. These wrist cuffs 254 areof identical structure. as that shown and disclosed in our saidcopending application Serial No. 757,581 so that they are not removablewhen the safety hooks 248 are hooked into the staples 252 thereon.

In assembled relation on the operators wrist, as dis- .closed in saidcopending application, the wrist cuff 254 ,is arcuately wrapped aroundthe wrist so as to overlap .the end to which the staple 252 is afiixed;The staple 252 extends through a selected elongated slot 256 formed inthe cuff 254 and the free, overlapping end of the cuff 254 is secured toan intermediate portion of the cuff by means of a buckle (not shown).

In order to actuate the micro switches 204 and 206 to closed positionand thereby energize the control circuit to facilitate energization ofthe magnetic coupling '70, the safety hooks 248 of each hook assembly244 are detachably latched on to their respective wrist cuif staples252. In latching the hook 248 onto staple 252, the staple 2 52, asdisclosed in said copending application, inwardly deflects the microswitch actuating flexible arm 246 and a shorter safety latching arm 258extending across the gap of hook 248 and affixed at one end to case 258adjacent and below arm 246. The staple 252 passes around the free end ofthe shorter lower arm 258 and thus permits this arm to deflect back toits original position closing the gap of hook 248 thereby lockinglylatching the staple 252 to the hook 248. The upper switch actuating arm246 is deflected by staple 252 from its undeflected position to adotted-line position indicated at B, FIGURE 8, where it is held bystaple 252 and depresses the'pin of micro switch 294 or 286 to actuatethe switch to a circuit closing position.

In accordance with said copending application, by attaching'the safetyhooks 248 to the wrist cuffs staples 252, the operator is unable tounwrap and remove the wrist cuffs 254 without first detaching the safetyhooks. By this structure, it will be appreciated that the micro switchesare actuated to a circuit energizing position only when the safety hooks248 are removably latched to their respective staples 252 and areactuated to a circuit de-energizing position when the hooks 248areunlatched from the staples 252.

In operation, the operator standing between the standard 210 and thepunch press 20 as viewed from FIGURE 1, is first required to affix thewrist cuffs 254 to his wrists and to latch the safety hook assemblies244 to the wrist cuff staples 252. This actuates micro switches 204 and206 to a circuit closed position and completes the control circuit 150to energize the relay solenoid coil 164 through a circuit that may betraced from the transformer secondary winding 156, through the closedmicro switches 204 and 206 and conductor 168, through solenoid coil 164,through conductor 166, through conductor 201, and contact 176, throughswitch blade 174, through conductor 200 and back to secondary 156.Energization of the solenoid coil 164 operates to move switch blade 174out of engagement with contact 176 so as to shunt a relay holdingcurrent through resistance 199 as hereinbefore described.

Energization of solenoid coil 164 also moves switch blade 172 intoengagement with contact 178 to energize the primary winding 180 of stepdown transformer 182. This causes energization of the secondary Winding184 of transformer 182 to energize the magnetic coupling coils 94 and96.

V The energization of coils 94 and 96 attract the armature 98 ofmagnetic coupling 70 to the core 68. Rigid engagement of the armature 98with the core 68 establishes a connecting linkage between the foottreadle' 50 and the clutch 36, so as to facilitate operation of thelatter by selective depression of the treadle 50 as hereinbeforedescribed. The actuation of the clutch '36 couples flywheel 38 to crosshead 30 to transmit power from the motor 42 to reciprocate the crosshead 30.

As the cross head 30 descends, the connecting rod 228 is shifteddownwardly to rotate the rocking arm 220 about its pivotal axis 222.This motion draws safety cable 232 upwardly through the tubular guide238 so as to shorten the effective length of cable 232 and its branchcables 240 and 242.

Since branch cables 240 and 242 are aflixed to the safety hookassemblies 244, the movement of the cables 240 and 242 functions toforce-ably withdraw the operators hands from a dangerous position.

On the upward stroke of the cross head 30, the connecting rod 228rotates the rocking arm in a counterclockwise direction as viewed fromFIGURE 1 to slacken and provide for a greater effective length of cables240 and 242. Sufiicient slack is provided to allow free movement of theoperators hands for the removal and insertion of work pieces in thepunch press.

If for any reason the operator desires to leave the area adjacent thepunch press 20, he must initially unlatch the safety hooks 248 from thewrist cuffs 254. This serves to open the micro switches 204 and 206 tode-energize the control circuit 150 and thereby de-energize the magneticcoupling energizing coils 94 and 96 so as to render the punch pressinoperable by actuation of the foot pedal 50. Similarly, when theoperator omits to attach the safety hooks 248 to the cuffs 254, it willbe appreciated from the foregoing that the press cannot be renderedoperable by actuation of the foot pedal 50 and consequently requiringthe operator to attach the safety device 208 to his body before he canset the press in operation.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a power driven machine having a frame, a work holding bed mountedon said frame, a work forming element movable into and out of workingrelation with said bed, power means for driving said work formingelement, means operably connecting said power means with said workforming element including a clutch mechanism, and a manually operatedclutch operator for selectively actuating said clutch to control themovement of said work forming element by operatively connecting anddisconnecting said power means and said work forming element; theimprovement of: a safety device responsive to the movement of said workforming element for forceably withdrawing the hands of an operator to aplace of safety during movement of said work forming element in apredetermined direction and including motion transmitting means movablein response to the movement of said work forming element, a pair ofwrist cufis adapted to be removably fastened about the wrists of theoperator, hook means adapted to be detachably latched to said cuifs fordetachably securing said motion transmitting means thereto, means forpreventing said cuffs from being unwrapped when said motion transmittingmeans is secured to said cuffs by said hook means, an electromagneticcoupling operable to connect and disconnect said clutch and said clutchoperator, and means for energizing and deenergizing said coupling torespectively establish and disestablish operative connection of saidclutch operator with said clutch comprising electrical circuit meansincluding at least one circuit energizing electrical switch actuatableto circuit energizing position by latching said hook means to saidcuffs.

2. In a safety device for use in a power-driven machine having a powersupply source, a work forming element movable by power delivered fromsaid power source, a clutch mechanism operably connecting said workforming element to said power source and a manually operated clutchoperator for controlling the actuation of said clutch mechanism,comprising a pair of cuifs adapted to be retained about the wrists of anoperator, flexible connection means detachably latched to said cuffs andresponsive to movement of said work forming element for withdrawing thehands of the operator to a place of safety, an electromagnetic couplingdevice operable when energized to couple said clutch operator to saidclutch mechanism, and means for deenergizing said coupling devicewhenever said fiexible connection means are unlatched from said wristcuffs to thereby operably disconnect said clutch operator from saidclutch mechanism.

3. In a safety device for use in a power-driven machine having a powersupply source, a work forming element movable by power delivered fromsaid power source, a clutch mechanism operably connecting said workforming element to said power source and a manually operated clutchoperator for controlling the actuation of said clutch mechanism,comprising a pair of cuffs adapted to be retained about the wrists of anoperator, flexible cable connection means detachably latched to saidcuffs and responsive to movement of said work forming element forwithdrawing the hands of the operator to a place of safety, anelectromagnetic coupling device operable when energized to couple saidclutch operator to said clutch mechanism, electrical circuit means forenergizing said electromagnetic coupling device, at least one circuitenergizing switch in said circuit means, and means for opening andclosing said switch by respectively unlatching and latching said cableconnection means to said wrist cuffs.

References (Jited in the file of this patent UNITED STATES PATENTS786,473 Wenigmann Apr. 4, 1905 2,013,441 Gofi et al Sept. 3, 19352,199,501 MacBlane May 7, 1940 2,830,686 Blume et al Apr. 15, 1958FOREIGN PATENTS 652,103 Germany Oct. 25, 1937

